1. Field of the Invention
The present invention relates to a linear generator adapted to generate a voltage proportional to the speed of a movable member or rotor and enable the movable member to be smoothly moved.
2. Statement of Prior Art
As disclosed in U.S. Pat. No. 4,500,827, a linear generator according to a prior art is constituted in such a way that a yoke and permanent magnets are fixedly mounted to a reciprocating shaft to provide a movable member or rotor, and magnetic poles, bobbins and coils are disposed oppositely to said permanent magnets to provide a stator. In this instance, the length of one permanent magnet is selected to become half of the stroke of a shaft, and the respective magnets are spaced by the distance corresponding to the stroke of the shaft and juxtaposed with different polarities. The width of the magnetic poles and the coils is made equivalent to that of the permanent magnets.
The magnetic resistance in relation to a permanent magnet is the smallest one when the permanent magnet is displaced to the position opposite or facing the magnetic pole and the largest one when the permanent magnet is displaced to the position opposite or facing to the coil. Accordingly, as explained above, the arrangement of the permanent magnet, the magnetic pole and the coil according to a prior art causes the magnetic resistance to vary remarkably depending on the displacement of the permanent magnet and also causes the magnetic energy being stored in the air gap defined between the permanent magnet and the magnetic pole to vary so considerably that a big cogging force will be generated. The term "cogging force" is used herein to express thrust at the time of unloading. Consequently, the peak of the force for driving the movable member or rotor is so high that a driving source for high thrust will be necessitated.
The present invention has therefore as the subject to solve to eliminate the drawbacks caused by the prior art as above explained.